Recovery of gold and silver from refractory ores.



CHARLES senses, or Lennon, ENGLAND.

RECOVERY or GOLD Ann sitvmt monmsaacmom ORES.

No Drawing.

To all whom it may concern:

Be itknown that I, CHARLns Burrnns, a citizen of the United States ofAmerica, residing at London, England, have invented certain new anduseful Improvements in increased, time is saved and so is also thecyanid or other solvent which may be employed in the final recovery" ofthe precious metal.

The invention is based on a reaction which it has been found occurs whensulfid gold and silver ores, tellurids, and similar ores associatedwith, or not associated with, arsenic, antimony and the like are broughtinto intimate contact such as by agitation or otherwise with certainmetals such for example as aluminium, zinc, tin or palladium, in anyconvenient form, but preferably as metallic surfaces, in the presence ofcaustic soda or other caustic alkalis, either hot or cold, which resultsin such ores being decomposed and the metallic gold and silver beingfreed from combination with the sulfur or the like whereby they are incondition to be readily attacked or dissolved by potassium cyanid orother suitable solvents.

According to the invention, the ore is first finely crushed or ground inthe presence of a solution of caustic soda or other caustic alkali andthe solution with the ore is then run into tanks from which firstly theexcess of the solution may be decanted. The ore with sufficientelectrolyte consisting of the caustic soda solution (of say 3/10%strength) to form a thick pulp is then agitated in such tank, or it maybe in a separate tank or tube mill if the first is not provided with anagitator. Such agitating tank may be lined with one of the metalsreferred to, say aluminium or it may contain or carry blocks or platesof the metal, the agitating element being also preferably of the samemetal, viz., aluminum. Under these conditions an electric current is setup between the aluminum and the ore under treatment, the aluminum actingas the anode and the ore as the cathode, which latter,

Specification of Letters Patent.

probably principally throughthe agency of nascent hydrogen, is thensplit upinto its component parts, and the precious metals left free tobe acted onby cyanid or other suitable solvents;

The following equations will serve as eX- amples to illustrate thereactions involved 1n this process:

A. Argeatz'te, (Ag S.l) 2Al'-[-2NaOH+2H,O:Na Al O,+6H. e1i+sii.'s+6NaoH':

3Na S+6H O+6Ag Since there is always an excess of caustic alkalipresent, the H S is immediately transformed into sodium sulfid asfollows:

In this case some of the arsenic goes into the solution in the excess ofthe caustic alkali, but most of this will be precipitated out again bythe aluminum if the treatment is continued long enough. For purposes ofthe subsequent'cyanid treatment it is immaterial'which of the twocourses is followed by the arsenic.

U. Pymrgym'te, (A SbS The same remark will hold good here as appliesabove in the case of arsenic.

D. Gold tcllum'd, say, (AuTe From time to time the pulp is sampled andwhen decomposition is sufficiently complete, it is withdrawn, filterpressed and the caustic soda or like alkaline solution returned to thecrushing plant. The filter pressed ore is then with or without washing,extracted with cyanid solution by the wellknown cyanid process, or isotherwise treated with a suitable solvent, the gold or silver beingprecipitated by zinc in the usual way.

Patented July 14, 1914:.

Application filed August 28, 1912. Serial No. 717,499.

What I claim is: 1 1. The process of treating refractory gold and silverores which consists in subjecting said ores in a finely dividedCondition to the action of nascent hydrogen produced in solut-ion duringthe reaction.

2. The process of'treating refractory gold and silver ores whichconsists in agitating the said ore whereby it is subjected to the actionof nascent hydrogen produced in the solution of which the ore forms apart dur ing the reaction.

8. The process of treating refractory gold and silver ores consisting insubjecting the gold to the action of a metal in the presence of causticalkali.

4:. The process of treating refractory gold and silver ores consistingin subjecting the ore in the presence of a metal having the property forthe required reaction of aluminium to the action of caustic alkali.

5. The process of treating refractory gold and silver ores consisting insubjecting the ore to the action of metallic aluminium in the presenceof caustic alkali.

6. The process of treating refractory gold and silver ores consisting insubjecting the ore to the action of metallic aluminium in the presenceof a solution of caustic alkali.

.7; The process oftreating refractory gold and silver ores consisting insubjecting the ore'to the action of a metal by agitation in the presenceof caustic alkali.

8. The process of recovering gold and silver from refractory ores,consisting in crushing the ore in the presence of a solution of causticalkali, then agitating the ore with suflicient of the solution to form athick pulp in the presence of a metal, then extracting the decomposedresidue from the alkali solution, and then subjecting such residue tothe action of a solvent to extract the precious metal.

9. The process of recovering gold and silver from refractory ores,consisting in crushing the ore in the presence of a solution ofcausticalkali, then agitating theore with sufiicient of the solution toform a thick pulp in the presence of a metal having the properties fortherequired reaction of aluminium, then filter pressing thedecomposedresidue to extract it from the alkaline solution,

and then subjecting such residue from the alkaline solution, and thensubjecting such residue to the action of a solvent to extract theprecious metal. i

10. The process of recovering gold and silver from refractory. ores,consisting in crushing the ore in the presence of a solution of causticalkali then agitating the ore with sufficient of the solution to form athick pulp in the presence of fixed and moving.

surfaces of a metal having the properties for the required reaction ofaluminium, then extracting the decomposed residue from the alkalinesolution, then subjecting such residue to the action of a solvent toextract the precious metal and then precipitating the latter. x

.In witness whereof I have hereunto set my hand in the presence of twosubscribing witnesses. p

7 CHARLES BUTTERS. Witnesses:

M. C. HUMPI-IRIES, ALLEN CARY J ONES.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner 01' Patents,

Washington, D. 0. i

